Background and Aims: Total hip arthroplasty (THA) is a common orthopedic surgery. The main focus in the research of THA is immune responses in these patients following the blood transfusion.Therefore, in this study, we evaluated the immune modulation indexes such as T cell amplification, Tcell surface markers and also production of cytokines in the patients undergoing THA surgery following blood transfusion.
Materials and Methods: A total of 30 patients referred to Imam Hussein Hospital for THA surgery were included in the study between May 2015 to May 2016. Transfusions of 500 ml allogeneic red blood were done during and immediately after recovery of THA operation. Along with pre- and post-operation, immune modulatory effects of transfusion, including proliferation of T lymphocyte, secretion of T cell cytokines such as interferon gamma (IFN-γ), Interleukin(IL)-4 and expression of T lymphocyte surface markers such as human leukocyte antigen D related (HLA-DR) and CD25 were evaluated. 
Results: Blood transfusion induced the expression of CD25 and HLA-DR markers in the THA patients. Blood transfusion also increased the secretion of IL-4 in post-operative stages in the THA patients. Results showed the increased IL-4 levels after blood transfusion. Whereas the levels of secretion in INF- γ were decreased after blood transfusion.
Conclusions: Allogeneic blood transfusion in the patients with the THA induced a cascade of immune and inflammatory responses, including increasing in T cell amplification and change in the secretion of interleukins that causes a modulation of immune responses. Further investigations should be performed to verify this hypothesis.